Injection pump



U. ALDINGER INJECTION PUMP Filed April 16, 1958 lmlmmm||mm March 15, 1960 United States Patent f "2,928,352 Y 1 :INJECTION PUMP Ulrich .Aldiuger, Stuttgart, Germanyaass'iguor to {Rob'et Bosch G.m.b.`H., Stuttgart, Germany Application-April i115, 1958,5Se'lil Ni). 729,015 Claims priority, application Germany.'April iN717, r1.9157 L11 Claims. XGL MBH-37) The present invention relates to injection pumps.

As is well known, 'injection .pumps are used 'with internal combustion 4engines -for supplying fuel Ato the cylinders of the engine to vbe burned therein.

At the .present time certain types of injection pumps have certain disadvantages. v For example, Vin certain types of pumps it is not possiblepto vary the cross section of the paths through which` the Afuel 'lows in the pump., so that the pumps are not as flexible as desired and cannot adapt themselves :readily to different operating conditions. Also, the .leakage losses of the .known injection .pumps are .unfavorable and the .pumps .are .not capable .of controlling the amounts offuel delivered toV thecylin- -ders with the high degree of .precision'by which i'sdesired. .Moreoven in .injection pumps which .are known .atthe .present time .the reciprocating masses are .larger than desired.

A@ne of the objects oft-he present .invention isto .overcome the above drawbacks -b-y .providing an injection pump which is capable of beingadjustedso as to :regulate the cross section -of passages through which .fuel .flows in the pump.

Another object of the present invent-ion is to reduce undesirable leakage losses .as well fas to .reducevthe .size of reciprocating masses, as compared to known injection pumps. l

Also, it is an object yoffthe present invention toprov-ide an injection pump which can produce `very,precisely regulated amounts of fuel to be delivered f-to the-engine.

Furthermore, it is an object of the present invent-ion to provide an injection pump composed of .simple and ruggedly constructed elements which 4are very reliable in operation. .Y

With the above objects -in View the .present invention includes in an injection pump yan .elongated hollow .first pump .member `and a vvi'irst guidemea-ns guiding the .rst

, pump member for reciprocating .axial movement .between a. suction dead center position, at :the end of the Vsuction stroke of the first pump member, and a pressure dead center position, at the fend of a pressure stroke of the first pump member. A second hollow elongated pump member is provided with an 'interior which defines at least part of fa pumping chamber, vand this-second pump member has an open end directed toward the first pump member and communicating with the pumping chamber formed in part at least by the :interior'of the second pump member. A second guide means .guides vthe second pump member for axial reciprocating movement vand positions the second pump member in the path of. 'movement of the first pump member from vits vsuction dead 'center position to its pressure -rdead `center .position f'so that 'during movement of 'the rst pump member toward 'its pressure Vdead 'center position :it 'engages and `'moves the second pump member, and lthe open fend of this second pump member is closed by :the trst pump member when theY latter engages the Second lpurrip member. A'n urging lmeans such as a spring cooperates with vthesecond pump 2,928,352 Patented Mar. 15, 1960 'member for urging the same toward the rs't pump .member, 'and in accordance with 'the Vpresent invention a 'stop 'means isf provided to limit the vmovement vof the second member by theurgin'g means 'toward the first pump 'meniberto an end position where the second pump fmem- Lber is spaced from the Vfirstv pump'member "while the latter 'continues to move jto vand from its suction dead center position so as to provide 'between the pump members fa :gap through which fuel ows into VVand out ofthe pumping chamber. Y j

The novel features `which 'are consideredl asfch'aracteristie for the 'invention are'set forthinfparticular in the appended claims. The invention itself, howevenbothas `t`o its construction 'and its method of operation, vtgetlier with additional objects and advantages thereof, will 'be 4best vunderstood 'from the 'following description of speci'c' embodiments when read in connection with the a'c`- V"compatrying drawings, `irrwhieh:

IFig. l shows a partly "schematic axial sectional view of 'an injectionpuinp Constructed according to the ,present j .,.inve'ntiom -the parts being shown in Fig. l at the suction dead centerposition of the pump; and

Fig. v2 Vfragmentarily illustrates't'ne structure of 'Fig l andshows the parts at the pressure dead center position. t

Referring to Fig. .1, it will be seenfthat the injection pump illustrated therein includes an'el'ongated hollow .pumpmember 3 which also functionsy as a distributor'in that 'this elongated hollow pump member 3-'is formed with an opening 33 passing through ,its wall and comlmunic'ating through passages described below `with 'the several cylinders ofk Vthe engine. This elongated hollow pump .member 3 cooperates with theV second elongated hollow pump member 4 which is coaxial with the pump member-3 `and which has ahollow interior deninglpart of a pumping chamber. It will be noted that the bottom' vend of the pump member 4, as viewed in Figs., :l and-2,

which is directed toward the pump member?? .is yopen.

The elongated hollow pump member 3 is connected at its bottom end, as viewed in Figs. l and'2, with a drive which both rotates and axially reciprocates lthe pum-p member 3. As is diagrammatically shown in Fig. .1, the

injection vpump includes a plurality of rollers 10.`which are supported for 'rotation about 'station-ary axes, respectively, and a drive shaft 5 is rotated and is .fixed with a cam 7 having downwardly directed camm-ing portions which. cooperate with 'the rollers 10 so that'during .rotation of the-drive shaft .5 the latter 'together with `the cam 7 reciprocate as well as rotate, the reciprocation resulting from lthe Vcooperationof the downwardly direc-ted annular camming surface of the cam 7 with the rollers liti. The cam 7 reciprocates during each of .its revolutions anumber of times equa-l to the number of cylinders ofthe engine.

A The elongated -`hollow pump member 3 ycarries Yat .its bottom end across pin 6 which extends transversely 'through and beyond the pumpl member 3, and the 'free ends 'of the cross pin 6 which are respectively Alocated laterally beyond the exterior surface of the hollow pump The `injection pump includes a support or housing 1,

and a spring 8 is'coiled about the pump member i3 'd bears with its Vtop end against a surface'of the statlonry V support 1. At its bottom end the spring 8 bearsagist the .race ring of a thrust ball bearing 9, so 'that the'spring #8 :serves -to maintain the cam 7 inenga'gemntwithfhe rollers while at the same time freeing the cam 7 forV rotation with respect to the spring 8. 'Y A plug 14 is pressed into the bottom end of the elon gated hollow pump member 3, as viewed in Figs. 1 and 2, and this plug 14 is formed with a transverse Vbore through which the pin 6 passes. The plug 14 fixedly carries at its top surface a rod 18 which extends axially along theinterior of the hollow pump member 3,Y anda coil spring is coiled Yabout this rod and bears with its bottomend against the plug member 1`4. `At its." top end the spring 15 bears against a valve member 16 which is pressed by the spring 15 into engagement VwithY a valve seat formed by an annular shoulder in the interior of,v

the elongated hollow pump member,3,.this valve member 16 being formed with a plurality of. radial elongated fins fabove the portion of the'valvef member which engages Vthe valve seat, so that when the valve member 16 is located in the pump member 3 at a position below the valve seat of the pump member 3 the fuel may flow past the valve member 16 axially .along the interior of thev pump member 3. 'Ihe rod 18 limits the extent of opening movement of the valve member 16, and when the latter valve memberis in a valve opening position p the fuel may flow to the opening 33 of the pump member 3, and from this opening 33 the fuelis distributed'` to the several cylinders. Above'the valve seat which cooperates with the valve member 16 the elongated hollow` pump member 3 is formed with a plurality of openings 24 which lpass through the wall of the pump member 3 and which communicate at their outer ends with pumping chamber 31 and forming an urging means for urging the pumping member 4 toward the pump member 3. The bottom end of the spring 27 bears against an inner annular shoulder of the pumping member 4 for urging the latter downwardlytoward the pump member 3. The guide member 25 is guided itself in the interior of the housing 1 by an inner cylindrical surface thereof located next to the plug 30, andthe spring 27 maintains Y the top wall of the guide `member 25 `in engagement with the bottom surface of the plug 30, as viewedin Fig. l. v

In accordance with the present invention an adjustable stop means is provided for limiting the movement of the pumprnember V4 toward the purnpmember 3, both of these pumpmembers being coaxial. f" This stop means includes an elongated hollow sleeve' 87 having at its bottom end an inwardly directed annular flange 89 which is engaged by an outwardly directed annular flange 90 of the pump Ymember 4 so as to limit the movement of the' pump member 4 by the spring 27 to an end position of the pump-member 4which is illustrated in Fig. 1. Therange 89 is formed with an upwardly directed frusto conical surface'engaged by a downwardly directed frustoconical surface'of the flange 90, and these frustoconical surfaces mate with each other and form a'uid-tight engagement between" the pump member 4 and the stop member 87. j Y

`At its open end which is directed toward the pump v member 3, the pump member 4 is formed with a second an annular groove 29 formed in the exteriorsurface of t the pump member 3.

A suitable guide means is provided for guiding the pump member 3 for axial Yreciprocating movement, and this guide means includesran elongated hollow cylindrical member 72 having Van interior surface which isdirected toward` an exterior surface of the pump member3`.\"1`he exterior surface of the pump member 3 is slidable along the interior surface of the cylindrical guide member 72. This 'guide member 72 is formed with a plurality of openings 73 corresponding to the number of cylinders and distributed about the axis of the cylindrical guide member 72, so that during the rotary and reciprocating movement of the member 3 the opening 33` thereof successively communicates with the several openings 73 so as to deliver fuel thereto. These openings 73 respectively communicate with passages '74 which respectively lead to the several cylinders, so that in this way the fuel` is` delivered by the injection pump to the several cylinders, One of the passages 74 is illustrated in Figl'.'` p. The cylindrical guide member 72 is furthermore formed with a plurality ofoverllow openings 75which cooperate with the annular groove 29of the pump member 3. The cylindrical guide ,member 72 is carried'by the support 1 and has an exterior surface directed toward and located next to an interior surface of the support 1, and one of these surfaces is formed with a plurality of passages 77 which respectively communicate with the over- `ilow openings 75. In the particular example illustrated in the drawings, the exterior surface of the cylindrical guide member 72 is formed with the axial grooves 77 which respectively `extend downwardly from the over-- flow opening 75' into the low pressure chamber of the injection pump which houses the spring 8. This low pressure chamber ofthe injection pump which houses the spring 8 as well as the cam drivemcomr'nunicates throughy a conduit 78 Vwith the supply tankA 35 from l vis directed toward'the pump member 3 cooperates with a frustoconical annular surface 92 which is separated from the flange.90 by an annular cutout 91` formed at the exterior of the' pump member 4, and this frustoconical surface 92 at the open end of the pump member 4 which frustoconical surface 93 located at the top end "efV the elongated hollow pump member 3, and the frustoconical surface of flange 90` as well as the frustoconical surface j 92 of the pump member 4 form part of the same cone.

-The surfaces 92 and 93 `also have a fluid-tight engagementwitheach other, so that the cooperation of the flange 90 with theflange 89`serves to separate the inlet pump chamber` 95'from-the space 94 dened between 'the stop member 87 and the pump member 4, while the Veooperationrof the `surfaces 92 and 93 with each other serves to ,separate` the pump chamber 31 from the inlet chamber `95 `and the space 94.

Vwhich fuel is pumped to the injection pump by a supply t, t

pump 36. n

Thesecond elongated hollow Apump member 4 is also .guided by a suitable guide meansjfor axial reciprocating movemennand .this guide means includes an elongated sleeve 25. which has located in its interior an end lplate 26 which cooperates with the upper end of a spring'27 lafeslinfthe iuteriligf the .member 4. which .denes the 'the rod 100 for turning movement about its axis.

As is `apparent from Fig. 1, the limiting of the movement of the pump member 4 by the stop member 87 to the end position of the pump member 4` shown in Fig. 1 provides at the suction `dead center position of the pump member 3, which is illustrated in Figi l, a gap between the pump members 3 and 4, and the fuel under pressure in the inlet vchamber of the pump can flow from this inlet chamber 95 through the gap` between pump members 3 and 4 intothe pumping chamber 31 through the open end of the pum-p member 4 which vis directed toward the pump member 3.' In accordance with the present invention an'adjusting meanscooperates with the stop means provided by the `sleeve 87 for adjusting the position of the latter along `the axis of the pump member 3, so that this way the size of the gap between the pump members 3 and 4` at the suction dead 'center position of the pump member `3 may 'be regulated. This adjusting means includes a pin/98 which extends into an opening of the sleeve 87, and this pin 98 is fixed eccentrically to the left endl of a rod 100 provided inter'- mediate` its ends with a'collar 101 fixed to the rod 100 the mannershown in Fig.fl,.this sleeveA 102 supporting 99 is fixed to the outer end of the rod A1.00, so that by turning the lever 99 the eccentric pin 98 will turn to regulate the elevation of the stop member 87. This stop mem- -ben is capable of `turning about its axis during turn t A lever x arguement-a artis. Thus, it is possible with this :structure 'toradjust ythe maximum sizeof the gap between membershnd 4. .As vis'evident from Fig. 2 which shows fthe' pump :member :3 atsits pressure dead center position, this-pump member :3 during its pressure stroke approaches iand engages Ythe pump member 4 to move the latterraXiall-y againstlthe 'force of the spring 27, while during imovement "of the pump member 3 from the position of .Fig 2 toward the pos'ition of Fig. 1 the pump member f4 willbeiengaged lbytthe stop member S7 to prevent continued -'movement of the pump member 4 with the pump'meinber 3 while `the iatter continues to moveto and fromithesuctiondead center position thereof shown in Fig. '1. rPhe lever'lis connectedthrough any suitable linkage to 'a manuallyfen- Agageable member'so that the operator may turn the lever '99 through thislinkage in order toY adjust the elevation Yof the sleeve 87. f

As was pointed out above, the pump 36 draws the fuel from the tank .35, and this pump 36 pumps the fuel under pressure through a filter 37 to a supply conduit 43 which supplies the fuel to the injection pump,the excess fuel ilowing through an overow valve 39 from the filter 37 'bac'kto the tank 35. The conduit 43 delivers the fuel to a passage 1&9 of the injection pump, and this passage 1&9 communicates through a passage 110 with the inlet 'chamber 95 referred to above. The cross section of the passage 110 may be regulated by an axially movable pin 112 which is guided Vfor axial movement by suitable bores or" the'housing V1 and which extends across the interior of the passage 11 ln the passage 11d the pin 112. is provided with lan annular `V-shaped groove, so that by varying the axial position of the pin 112 the cross sectional area of the passage 110 through which the fuel ilows may be regulated, and in this way an adjustable throttle kfor the supply of the fuel to the inlet chamber 95 is provided. The throttle member 112 separates the passages 109 and 110 from'geach other, and the throttle member 112 isA guided in the axial bore 113 kof the housing-1, this bore 113 being closed at its top end, as viewed 'in Fig. l, by a plug 114 which cooperates with a sealing lring 115. At its bottom end, as viewed in Fig. l, which extends `into the interior of the injection pump, the throttling rod 112 is connected in a known Way with `a governor which may be'adjusted by the operator at will so las to regulate the position ofthe'rod 112.

As is shown in Fig. 1, the space9t lbetween the pump .member 4 and thestop member v3'7 communicates through a passage'117 `with the passage 169 to which the :fuel is delivered from the conduit 43. Y

Thus, vwhen the pump member 3 moves along its suction stroke to the lposition of the pump member 3 shown in Fig. l, there comes a time when :the pump member 4 is prevented .frommov'ing with .the pump member 3 by engagement with 'the flange 89, and at this time the fuel iiows'from the .inlet chamber 95 into the pumping chamber 31. ,At the beginning of the pressure stroke of the pump member 3, the :volume of `the inlet chamber 95 .is reduced'by the movement of the pump member 3 until the latter engages the pump member 4, and this increase in the pressure ofthe fuel in Vthe n inlet chamber 95 which communicates with the pump chamber 31 is of advantage since it enables the upper speed limit to be raised, this `upper speed limit being determined by the pressure of the fuel in the pump chamber 31 during the lilling of this pump chamber.

,As soon as the pump member 3 moves the pump member t away from the flange 89, the `pump chamber v31 `is closed and the valve then opens dueto the diminishing volume of the pump chamber 31 -and Ythe corresponding ypressure which serves ;tol open the valve `member 16 tngaiust tthe sforee :the :spring '15., :so .that the Vfuel liberi flows :to v:the .distributor opening 33 'o'f the` pump-f member 1:3 to 'be r c'lelivered from :the opening P33 .successively throughrthefseveral cylinders .through thesever'al .passage :means 73, '7.4. The :delivery of;the"fuel fromthetpump member 3 to a particular cylinder at any given'm'oment continues until'the zcontinuedmovement of the pump rm'ember .Sifalongltspressure :stroke places the annular 4groove'ltw in lte'n'ga'g'ementrwithfthe overtlow openings '75. :At this-.itirn'ethe .ffuel can flow from the interior of the pumpfm'ember 33-.througl1'th'e overliow opening 75 and -along the g'rooves'7-7 to` thejlow pressure chamber which `"communieates through 'the conduit 78 with the tank 35, Lsofthatvvhen the groove Z9 communicates with the overiiow opening '-75-'the.`d`eliveryof`the fuel to a given cylinderso'l' theengineis'tops.. BecauseV of the drop in pressure vprovided in the interior of the pump member 3 at the moment whenfthegroove'29 communicates with the overllowopening the spring 15 returns the valve 16 to its closed position, and' any fuel remainingin the pump mem- 'ber 3 from this 'moment on during the continued move- Vment of the pump member 3 simply flows through the overflow openings back to the tank 35. Moreover, during the pressure stroke of the pump 3, from the moment that this pump member 3 engages the pump member 4 and moves thelatter awayA from the ilange 89, the volumes of the inlet chamber 'and the space 94 are also reduced,

and the -fuel displaced from the chamber 95 and the space 94 in this way Hows through the passage 117 back tothe inlet passage 109. This passage 117 providesfor the returnflow of .thefuel at smaller resistance .thanthe passage Vwith the tnrotthng member 112.

` The above operations takeplace during the pressure stroke of the pump. During .the succeeding suction stroke, which is to say .during the return of the parts Vfrom .the .positions of Fig. 2 tothe .position of Fig. 1, fuel is sucked .through .the passage 117 trom the passage 169 into the space Y94 andchamber .95 until 'the .ilange A9i) of the pump .member 4engages the flange 890i the stop member 87 soasto separate the space 94 from the .inlet pump chamberV .95. Then, during the continued 4movement of the pump .member 3 'by itself along Vits .suction stroke to the suction-dead center position thereof 4shown inFig. .1, .the .fuel .flows throughthe passages 109- .and .110 past the throttling member 112 into thezinlet lchamber `95 .from Where vthe fuel liowsinto Vthe pumping .chamberl through the gap between the pump members 3 and 4. The engagement .of theilange '96 with ange v 89 provides the furtneradvantage of Vseparating the space 94 from thechamber 95 .so as .to greatly reduce the free space inthe interior of the pump to which fuel` under f ,pressureiis delivered, thisV space being limited only by the passage 11d-and the inlet-chamber95.

By actuation of the lever 99, it is possible .for .the

'operator toposition the -stop member 87' during starting Vof the engine at a location which permits the Yengine `to' .be provided at starting thereof Vwith amounts of ffuel which exceed the full load amounts, yso that the engine .can be properly started.

The adjustment of the amounts of -fuel delivered by Y -the1pump during the operation of the engine 'according to the loading thereof is provided with the aid of the vthrottling member 112. According to the axial .position vof .this throttlingmember, the cross .sectional larea4 of .the 'passage 109, 110 isincreased or decreased. The .smaller 4this cross sectional area the smaller the amount of fuel which can flow through the gap between members 3 and 4 during 'the suction stroke 'of member 3, the length ofV YWhile the invention has been illustrated and described as embodied in adjustable injection pumps, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present i invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention nthatothei's can` intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by LettersA Patent is: Y

1. In an injection pump, in combination, an

elongated hollow first pump member; first guide means guiding said first pump member for reciprocatingfaxial'movement betweenla suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center' position, at the 'eend of a pressure stroke of Vsaid firstpump member; a second hollowelongated pump member having a Vfirst open V'end directed toward said first 'pump member and a second Open end; second guide means'surrounding and slidingly engaging said second pump member and having aclosed end spaced from said second open end of said second hollow elongated pump member and defining a pumping chainber, said second guide means guiding said second pump member for axial reciprocating movement and positioning said second pump member in the path of movementof said first pump member from its suction dead center position to its pressure dead centerposition so that during movement of said first pump member along its pressure stroke toward its pressure dead center position it engages and moves said second pump member toward said closed end to provide for a pumping action, the first open end of the latter being `closed by said firstpump member when the AlatterV engages said second pump member;- urgingmeans cooperating with said second pump member for urging the latter toward-said first pump member; stop means limiting the movement of said second pump member by said urging meanstoward said first pump -member toA an end position while the first pump member continues `to'move to and from its suctionrdead center positionso as-to provide between said pump members a gap;V fluid inlet means communicating "with said gap through which uid mayfow into said pumping cham ber when said second pump member-is in said end position; and valve means communicating with said pumping chamber to discharge fiuid therefrom during said pres-` sure stroke of said first pump member aftersaid gap 2. in an injection pump, in combination, an elongated hollow first pump member; first guide means guiding said first pump member for reciprocating axial movement between a suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center position, at the end of `a pressure stroke of said first pump member; a second hollow elongated pumpV member having a first open end directed toward said first pump member and a 'second open end; second guide means surrounding and slidingly engaging said second pump member and having a closed end spaced from said second open end of said second hollow elongated pump member and defining a pumping chamber, said second guide means guiding said second pump member-for axial movement and positioning said second pump member coaXiallywith said first pump member in the path of movement of the latter from its suction dead center position to its pressure dead center position so that duringmovement of saidfirst pump member toward its pressure dead center position it engages and moves .said second'pump. member towardsaid closed end vto provide fora pumping action, the first open end of the latter being closed by said first pump member when the latter engages` said second pump member; urging means .cooperating with said' second pump member for urging the lattervtoward said first pump member; stop means limiting the movement of said second pump member by Vsaidurging means `toward said first pump member to an end position where said second pump member is spaced from said first pumprmember while the latter continues to move to and ,from its suction deadcenter position so as Vto provide between` said pump Vmembers, a gap; fluid t discharge iiuid therefrom duringlsaid pressure stroke of Y Ving with said gap through which `iiuid may flow into said said= first-'pump member after said gap is closed.

3. Inan injection pump, in combination, an elongated hollow first `pump member; first guide means guiding said first pump member for reciprocating axial movement betweena suction dead center position, at the end of a suction stroke of said first pump member, and a pressure Vdead `center position, at the end of a pressure stroke of said first pump member; a second hollow elongated pump member having a first open end directed 'toward said first pump member and a second open end;

second guide means surrounding and slidingly engaging said second pump member and having ja closed end spaced from said second open end of said second hollow elongated pump member and defining a pumping chamber, said second guide means guiding said second pumpi member for axial reciprocating movement and positioning said second pump member in thepath of movement of said frstpump member from its" suction dead center position to its pressure dead center position so that during movement of said first pump member along its pressurrevs'troke toward lits pressure dead center position it engages and moves said second pump member toward said closed end to provide for a pumping faction, the first open end of the ,latter being closed by said first pump member when the latter engages said second pump member; urging `means cooperating with said second pump member for urging the latter toward said first pump member;stop means limiting the movement of said second pump member by said urging means toward said first vpump member Vto an end position where said second pump member is `spaced from said first vpump member while the `latter continues to move toand from its suction dead center position so as to provide between said pump membersa gap; fluid inlet means communicatpumping chamber when said second pump member is in said end position; and valve means communicating with .said pumping chamber to discharge'fiuid therefrom during said pressurefstroke of said first pump member after said gap is closed;`and adjusting means` cooperatingwith said stop means for adjusting the position thereof along` Ythe axis of said first pump `member, so that the maximum size of said `gap may be adjusted and so that the moment during the pressure stroke of said rst pump member that the latter engages said second pump member and the moment during the suction stroke of said first pump member that the latter leaves said second pump member may be adjusted.

4. In an injection pump, in combination, an elongated hollow first pump member; first guide means guiding said first pump member for reciprocating axial movement between a suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center position, at the end of a pressure stroke of said first pump member; a second hollow elongated` pump member having a first open end directed toward,V said first pump member and a second open end; second guide means surrounding and slidingly engaging said :second pump member 'and 'having a fclosed yend spaced from Isaid second open vend fof said second hollow ielongated pump member and defining a pumping chamber, said second guide means :guiding said secondY pump member for axial reciprocating movement tand positioning said second vpump member fin the path 'of vvmovement of said first pump member from its suction deadcenter position to its pressure dead center position 'so that'during movement of said first pump member along `its pressure stroke toward its pressure dead center position it engages and moves said second pump member toward said closed end to provide for a pumping action, the -first open fend of'the latter :being .closed by said `first pump member when the latter .engages'said secondpump member; urging means cooperating Withrsaid :second .pump member for urgingy the `latter ltoward said first pump member; stop means .limiting vthe movement of said second pump 'member by said urging means toward fsaid first pump member to an end position Where said ksecond pump member is spaced from said first pump ymember `while the lattter4 continues to moveto and from its suction dead center ,position so as Ytolprovide between said pump members 'a gap., said stop means having .an annular frustoconical surface engaged by` said second pump member and the latter y'havingan annular frustoconical surface mating with and engaging said annular surface -of said stop means; fiuid inlet vmeans communicating with said gap through vwhich -fiuidmay fiow into lsaid pumping chamber when said second @pump member -is in said end position; and valve means communicating 'with said pumping chamber to discharge fluid therefrom 'during said Vpressure stroke of said .first pump member after said gap is closed.`

5. In an injection pump, in combination, an elongated hollow first pump member; first guide means guiding said 'first pump member for reciprocatingv axial :movement be- '.twe'e'n a'suction dead center position, at lthe" end of asuetion stroke of said first pumpmembenand a pressure dead fcenter position, at the end of a `pressure stroke of 'said first pump member; a `second hollow kelongated pump :member having a first open end directed toward said 'first .pump member; a second open end; second guide 'means surrounding and 'slidingly vengaging said second `.pump member and having a closed end spaced from said second open end of said second hollow elongated pump ember and defining a pumping'chamber, said second Aguide means guiding said second pump member for axial "movement and positioning said second pump member yc'o'axially with said first pump member :in the 'path of movement of the .latter from its .suction `dead center position to its pressure dead center position so that during movement of said first pumpV member vtoward fits pressure'dead center position Vit engages and moves `said second pump member toward said closed end .to provide for a pumping action, the ,first open end of 'the latter b'eing closed by said first pump member when the'la'tter lengages said second pump member; urging `means cooperating'with said second pump member for Vurging the latter toward said first pump member; and stop means `limiting the movement of said second pump member by said :urging .means toward said first pump member to `an end position where said second pump member is .spaced from said first pump member while the latter continues lto move to and from its suction dead centerpositionso as to provide between said pump members a gap, saidstop means having an annular frustoconical surface Yengaged by said second pump member andsaid second pump member having an annular frustoconical surface `:mating ywith and engaging said annular surface of said stop means when the latter locates said second pump member in said end position thereof, and said first pump .member having an annular frustoconical surface and said second pump member having an annular frustoconical surface located at said open end thereof and Vengaging rsai'd :annular frustoconical 'surface gf said V,first 'pump fonemas' ymember when the latterlis inengagement with saidsecond pump member; fluid inlet means communicating with` said gap through which fluid lmay fiow .into said pumping chamber Vwhen said second pump member is in fsaid zend position; rand valve means communicating with saidv pumping chamber to discharge -fiuidv therefrom during said pressure stroke of said' first pump member after said :gap is closed.

v6. In an injection pump, in combination, an elongated :hollow first pump member; first guide meansv guidingsaid first pump member for reciprocating axial movement be tween a suction `dead center position, at the -end of a suction stroke of said first pump member, and a pressure :coaxially with said first pump member in the pathv of movement of the latter from its suction dead center posi` :tion to its pressure dead center position .so that during movement of said first .pump member toward its :pressure dead lcenter position it engages and Vmoves said second pump membertoward said closed vend ,to provide for :a pumping action, the first open end of vthe latter being closed by said first pump member when'the latter engages said second pump member; urging means cooperat- .ingwith said -second pumpmember for urging the latter toward said first pump member; stop means .limiting the movement of said second pump member by said urging means towardsaidefirst pump member toan end position 'where said second pump member is spaced from .'said' first pump member while the latter Vcontinues to `move Vto and 'from its suction dead center positionso-as `to-provide ibetween said pump members a gap, said stopimeans having an annular frustoconical surface ,engaged by'said second pump member and said second pump member having an annular frustoconical. surface mating with and engaging said annular surface of said stop means when `rthe .latter locates said second pumpmember in said end position thereof, and said first pump member having an annular frustoconical surface and saidsecond pumpmember having an annular frustoconic'al surface locatedtat 1 :said .open end thereof and engaging said annular frustovconical-surface of said first pump member when the .latter is in engagement with said 'second pump member, said first-mentioned and second annular frustoconical-:surfaces of said second pump member forming part of the fsame cone; fluid inletV means communicating Vwith ,said

gap .through which fluid vmay flow yinto said pumping vchamber when said second pump member'is in said end positron; and valve means communicating-withsaidipump- ,ing chamber to discharge fluid therefrom during said .pressure 'stroke of said first pumpmember'aftersaid 'gap isrclosed.

7. In an injection pump, in combination, an elongated hollow first pump member; first guide means guiding said'v i' .first pump member for reciprocating axial movement between .asuction dead center position, at `the end of :a suction stroke of said first-'pump member, and a pressure dead center position, at the end of 1a pressure stroke of said first pump member; la second hollow elongated pump member having a first open end Ydirected `toward said'first pump member and a second open end; second guide means surrounding and slidinglyv engaging said second `pump member and having a closed end spaced from said second open -end `of said second hollow elongated :pump Amember and defining a pumping chamber, -said second guide .means guiding said second pump member for axial l I5 movement and .positioning .said second 4pump member Acog' "axially with said first pump member in the path of move said first pump member when the latter-engages said Ysecond pump member; urging means'coperating with said second pump member for urging the latter toward said first pump member; stop means limiting the movement of said second pump member by said urging means toward said first pump member to an end position where said second pump member is spaced from said first pump member while the latter continues to move to and from its suction dead center position so as to provide between said pump members a gap through which fuel flows into and out of said pumping chamber, said stop means having an annular frustoconical surface engaged byY said second` pump member and said secondupump member having an annularfrustoconical surface mating .with and engaging said annular surface of said stop means when the latter ,locates saidV second .pump member in said end` position thereof, and said first pump member having an conical surface of said first pump member when'the latterV Vcal surface engaged'by'saidzsecond pump memberand said'second` pump member having an annular v.frustoconical surface mating with and engaging said annular frustoconical surface of said stop `means whenthe latter i Y locates said second'pump member in said end'position thereof, said annular frustoconicalwsurfacesi of said stop means and said .second pump member having a` fluidtight engagement with each other; fluid inlet means communicating withsaid gap through which fluid may ow into said pumping chamber` when `said second pump mernber is in said end position; and valve means communicating with said pumping chamber to discharge fluid therefrom during said pressure stroke of said first pump member after said gap. is closed. Y

9. In an injection pump, in combinatioman elongated hollow first pump member; first guide means guiding said first pump member for: reciprocating axial movement `between aY suction dead center position,'at the end of a suction stroke of said firstpump member, and a pressure f guide means `guiding said second pump member for axial is in engagement with said second pump member, saidV first-mentioned and second annularfrustoconical surfaces of said second pump member forming part of the same cone, said second pump member being formed with an annular cutout located between and separating said first- Y mentioned and said second annular frustoconcal surfaces of said second pump member from each other; fluid inlet means communicating with said gap through 'which fluid Vmay flow into said pumping chamber when said lSecond first pump member for reciprocating axiall movement` between a suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center position, at the end of a pressure stroke of said first pump member; a second hollow elongated pump member having a Vfi'rstopen VYend directed toward saidfirst' pump member and a second open end; second guide means surroundingland slidingly engaging said second pump member and having a closed end spaced from said second open end of said second hollow elongated pump member and defining -a pumping chamber, said second guide means guiding said second pump member for axial reciprocating movement and positioning said second pump member in the path of movement of said first pump member from its suction dead center position to its pressure dead center position so that during movement of said first pump member along its pressure stroke toward its pressure dead'center position it engages and moves said second pump member toward said closed end to provide for a pumping action, the first open end of the latter being closed by said first pump member when the latter engages said second pump member; urging means cooperatingwith said second pump member for urging the latter toward said first pump member; stop means limiting the movement of said second pump member by said urging means toward saidV first pump member to an end position where said second ,pump` member is spaced from said first pump member while the latter continues to move to and from its suction dead center position so a's to provide between said pump members a gap through which fuel flows into and out of said pumping chamber, said stop means having` @annular frustoconireciprocating movement and positioning said second pump member in the path of movement of said first pump member from its suction dead center position to its pressure `dead center position so that during movement of said first pump member along its pressure stroke toward its pressure ^dead center position it engages and moves said Vsecond'pump member toward said closed endto provide for a pumping action, the first open end of the latter being closed by said first pumpmember when the latter l engages said second pumpmember; urgingmeans cooperating with said second pump member for`urging the `latter toward said firstpump. member; stop means limiting the movement of said second pump member by said urging means toward said first pump member to an end position where said second pump member isspaced from said first pump member while the latter continues to move to and `from itssuction dead center position so as to provide between `said pump members `a gap'through which fuel flows into `and out ofsaid pumping chamber, said stop means and said second pump member defining between themselves a space which 'surroundspsaid second pump memberand is located between the latter and said s top means; means `forming an inlet chamber of said injection pump to whichrfuel under pressure is supplied from a supply pump; passage means providing communicationbet'ween saidspaceand said inlet chamber; and valve means communicating vwithsaid pumping cham- -beruto` discharge fueltherefrom during said pressure stroke of said first pump member after said gap is closed. l0. In an `injection pump; having a low pressure chamber in combination, a cylindrical guide member having an exterior surface and formed with a plurality ofoverflow openings passing through the wall of said cylindrical guide member; a support supporting said guide member and having an inner surfacelocated next to and directed ltoward said. exterior surface of said guide member, one` said overflow openings of said guide member'during Aa predetermined part of the axialmovement of said first pump member, said guide member guiding said first pump, member for movement between a suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center position, at the end of a pressure stroke of said first pump member; a second hollow elongated pump member having a first open end directed toward said first pump member and a second open end; guide means surrounding and slidingly engaging said second pump member and having a closed end spaced from said second open end of said second hollow elongated pump member and defining a pumping chamber, said guide means guiding said second pump member for axial reciprocating movement and positioning said second pump member in the path of movement of said first pump member from its suction dead center position to its pressure dead center position so that during movement of said first pump member toward its pressure dead center position it engages and moves said second pump member toward said closed end to provide for a pumping action, the first open end of the latter being closed by said first pump member when the latter engagessaid second pump member; urging means cooperating with said second pump member for urging the latter toward said rst vpump member; stop means limiting the movement of said second pump member by said urging means toward said first pump member to an end position where said second pump member is spaced from said first pump member while the latter continues to move to and from its suction dead center position so as to provide between said pump members a gap; fiuid inlet means communicating with said gap through which uid may ow into said pumping chamber when said second pump member is in said end position; and valve means communicating with said pumping chamber to discharge fluid therefrom during said pressure stroke of said first pump member after said gap is closed.

11. In an injection pump, in combination, an elongated hollow first pump member; first guide means guiding said first pump member for reciprocating axial movement between a suction dead center position, at the end of a suction stroke of said first pump member, and a pressure dead center position, at the end of a pressure stroke of said first pump member; a second hollow elongated pump member having a first open end directed toward said ttl first pump member and a second open end; second guido i i means Vsurrounding and slidingly engaging said second pump member and having a closed .end spaced froml said second open end of said second hollow elongated pump member and defining a pumping chamber, saidsecond guide means guidingV said second pump member for axial reciprocating movement and positioning said second pump member in the path of movement of said first pump member from its suction dead center position to its pressure dead center position so that during movement of said first pump member along its pressure stroke toward its pressure dead center position it engages and moves said second pump member toward said closed end to provide for a pumping action, the first open end of the latter being closed by said first pump member when the latter engages said second pump member; urging means cooperating with said second pump member for urging r the latter toward said first pump member; stop means limiting the movement of said second pump membe by said urging means toward said first pump member to an end position where said second pump member is spaced from said first pump member while the latter continues to move to and from its suction dead center position so as to provide between said pump members a. gap; means forming a fuel inlet chamber of said injection pump communicating said gap so that fuel under pressure in said inlet chamber of said pump ows through said gap into said pumping chamber; adjustable means cooperating with said inlet chamberrfor regulating the cross sectional area thereof; and valve means communieating with said pumping chamber to discharge fuel'therefrom during said pressure stroke of said first pump member after said gap is closed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,810,376 Aldinger Oct. 22, 1957 FOREIGN PATENTS Y 628,132 Great Britain '-2 Aug. 23, 1949 

